A semiconductor light receiving apparatus plays important roles in fields of optical communications and measurements as a photoelectric converting apparatus. A typical construction of a conventional semiconductor light receiving apparatus is that, a photodiode chip such as PIN-photodiode is mounted on a carrier, which is fixed to a stem as one body, and a cap seals up these elements and is fixed to a stem. A cap has a flattened top and is provided with an opening at a center of a top. This is covered with a plate formed glass. In most cases, outer and inner surfaces of a glass and a light receiving surface are parallel to each other, and an input ray of light incidents normally to these surfaces.
In this construction, a portion of a ray is reflected at both surfaces of a plate formed glass and a light receiving of a photodiode chip. Consequently, a portion of an input ray returns to a light source. Moreover, when multiple reflections of a ray along a light path cannot be neglected, other portions of the input ray become delayed incidences to the light receiving surface of the chip. These phenomena cause noise on the output signal of the semiconductor light receiving apparatus.